Biomedical subjects

C Trillaud

Publications and source records attributed to C Trillaud.

4 recordsLinked to original sources

PubMed1992

Electrical impedance tomography. An improved design of voltmeter for semi-parallel data acquisition.

The design and implementation of high performance differential voltmeters for semi-parallel data acquisition are described. The general requirements and specific conditions encountered in electrical impedance tomography (EIT) for accurate measurements are analysed. The major parameters are common-mode rejection and bandwidth. A specific implementation of the voltmeters, with separate DC supplies and independent signal references, is described. This arrangement, in which each voltmeter follows the input signal, automatically cancels any common-mode voltage present at the input. The signal is fed to the remainder of the instrumentation through a transformer. The use of a reduced number of components contributes to the minimisation of the inter-channel variations. Furthermore, the geometrical distribution of the voltmeters around the object minimises the length of electrode wires, also reducing the input capacitance. The number of modular voltmeters and DC/DC converters is 32. The common-mode rejection of these voltmeters is greater than 72 dB in the frequency range 3.6-560 kHz. In conclusion, the proposed solution ensures a minimisation of common-mode errors and enables the use of a 250 kHz frequency.

Electric Conductivity↗

PubMed1992

Imaging the complex impedance in electrical impedance tomography.

Measuring the reactive component of the bio-impedance enables a full characterisation of the frequency response of a tissue. The amplitude of the reactive component is relatively small in the frequency range generally used in electrical impedance tomography (EIT). Its measurement is therefore more sensitive to errors. At higher frequencies, the amplitude of this component increases, which increases the signal-to-noise ratio. The stray capacitance, however, also increases and the front-end circuit must be designed carefully. The purpose of the present study is to show the feasibility of the collection of data at relatively high frequencies; 31.25 and 250 kHz were used. Both the real and reactive components were used to reconstruct images from capacitive targets. This study suggests that it may be possible to use multifrequency systems to determine the parameters of frequency loci and therefore tissue characterisation.

Electric Conductivity↗

PubMed1981

[Study, after stopping treatment, of the consequences of the injection of male hormones in mares on their social behavior and hierarchical position].

The androgenization of a more belonging to a social group where it held a stable hierarchic rank, or a mare recently admitted to this group, increases their status in the hierarchic order and the position acquired is subsequently maintained; in some cases, they continue to rise in the hierarchic order long after the injections of male hormones has been stopped. Some elements of the social behaviour of a stallion appear during the treatment; these elements may persist long after the mares have regained their female hormone balance, corroborated by the establishment of a standard pregnancy.

Aggression↗

PubMedDate not supplied

A high frequency electrical impedance tomograph using distributed parallel input channels.

Electrical Impedance Tomography (EIT) is an imaging technique based on multiple impedance measurements using electronically multiplexed surface electrodes. The present study describes an EIT prototype tomograph which uses two frequencies of applied signal: 31.25 kHz (within the frequency range originally used in early EIT studies) and 250 kHz. The use of the latter frequency was made possible as a result of several technical innovations including the use of separate groups of electrodes for current injection and for differential voltage measurement and the use of parallel input channels distributed around the object. In vitro images were successfully obtained using the system at the above two frequencies. It is concluded from this study that Electrical Impedance Tomography can be used at sufficiently high frequencies to enable bio-electrical tissue characterisation.

Electric Conductivity↗